As sociologist and network science pioneer Duncan Watts explains in Everything is obvious, the explanations that we give for the outcomes that we observe in life—explanation that seem obvious once we know the answer—are less useful than they seem.
The miraculous piece of human intelligence that enables us to solve these problems is what we call common sense. Common sense is so ordinary that we tend to notice it only when it’s missing, but it is absolutely essential to functioning in everyday life.
Common sense is how we know what to wear when we go to work in the morning, how to behave on the street or the subway, and how to maintain harmonious relationships with our friends and coworkers. It tells us when to obey the rules, when to quietly ignore them, and when to stand up and challenge the rules themselves. It is the essence of social intelligence, and is also deeply embedded in our legal system, in political philosophy, and in professional training.
For something we refer to so often, however, common sense is surprisingly hard to pin down. Roughly speaking, it is the loosely organized set of facts, observations, experiences, insights, and pieces of received wisdom that each of us accumulates over a lifetime, in the course of encountering, dealing with, and learning from, everyday situations.
Lack of common sense
People who lack common sense are a bit like the hapless robot in that they never seem to understand what it is that they should be paying attention to, and they never seem to understand what it is that they don’t understand.
And for exactly the same reason that programming robots is hard, it’s surprisingly hard to explain to someone lacking in common sense what it is that they’re doing wrong. You can take them back through various examples of when they said or did the wrong thing, and perhaps they’ll be able to avoid making exactly those errors again. But as soon as anything is different, they’re effectively back to square one.
Not common at all
As remarkable as it is, common sense exhibits some mysterious quirks, one of the most striking of which is how much it varies over time, and across cultures.
Common sense is ‘common’ only to the extent that two people share sufficiently similar social and cultural experiences. Common sense, in other words, depends on what the sociologist Harry Collins calls collective tacit knowledge, meaning that it is encoded in the social norms, customs, and practices of the world. According to Collins, the acquisition of this type of knowledge can be learned only by participating in society itself–and that’s why it is so hard to teach to machines.
Another important consequence of the socially embedded nature of common sense is that disagreements over matters of common sense can be surprisingly difficult to resolve.
The misuse of common sense
The fragmented, inconsistent, and even self-contradictory nature of common sense does not generally present a problem in our everyday lives. The reason is that everyday life is effectively broken up into small problems, grounded in very specific contexts that we can solve more or less independently of one another.
Under these circumstances, being able to connect out thought processes in a logical manner isn’t really the point. It doesn’t really matter that absence makes the heart grow fonder in one situation, and that out of sight is out of mind in the next. In any given situation we know the point we’re trying to make, or the decision we want to support, and we choose the appropriate piece of commonsense wisdom to apply to it.